Method of making resin coated pulpboard



H. c. HARVEY ET AL 1,351,177

METHOD OF MAKING RESIN COATED PULPBOARD March 29, 1932.

Filed Aug. 4, 1928 INVENTORS /-/4.0/.0 C HAer EY #05527 L. Baa/5e BY 0 (M ATTORN s Patented Mar. 29, 1932 UNITED STATES PATENT OFFICE HAROLD C. HARVEY, OF EWING TOWNSHIP, MERCER COUNTY, AND HUBEI BT L. BECKER,

OF HAMILTON TOWNSHIP, MERCER COUNTY, NEW JERSEY, ASSIGNORS TO THE c AGASOTE MILLIBOARD COMPANY, OF EWING TOWNSHIP, NEW JERSEY, A. CORPORA- TION OI NEW JERSEY METHOD MAKING RESIN COATED PULPBOABD Application filed August 4, 1928. Serial No. 297,533.

Our invention relates to pulp board containing a'fiuxing binder coated with artificial resin, and to a method of making the same.

Pulp board is usually made by running paper pulp, wood pulp, asbestos or the like into a mold and, by means of pressure, removing the majority of water (see, for instance, patent to D. M. Sutherland, J r., No. 1,272,566 dated July 16, 1918) and subsequen'tly drying out the remainder of the water by the application of heat, preferably in a suitably constructed dryer. There is usually added to the pulp, prior to shaping it in they mold, a suitable binder, either a fluxing binder or a non-fluxing binder.

Our invention relates to pulp board having added thereto a fluxing binder, for instance, the substance known in commerce as red 'acaroid gum which, we understand, is obtained from several species of the Xanthorrhoea tree, the use of which is described and claimed in our United States Patent No 1,651,388 dated December 6, 1927. In place of this material there may be used gilsonite, rosin, gumresins, mineral pitch or asphalt, although we prefer the red acaroid gum because it produces a board absorbing only a very small proportion of moisture and therefore suffering very little expansion and contraction because of atmospheric changes. When such a fiuxing binder is used, the board, after having been dried, is in what might be termed a spongy condition and we therefore apply to this unfinished board the term .sponge board. This board is subjected to heat and pressure to form a compacted board.

When pulp board containing a fiuxlng binder has been produced in the-manner herein above'described, namely, by first having the majority of the water removed by means of pressure from the material as it comes from the mold, and the remainder then removed by the application of heat to form sponge board, and such sponge board has been compacted by heat and pressure, it is a commercial article (except possibly for subsequent shaplng operations such as coating or bendlng) which has been on the market for some time. It is a firm compact board which pon a compacted board of this type, which we shall call a base board, we place one or more sheets of paper, referably at least three, or other suitable fi rous material, impregnated with a phenolic or other artificial resin of the class which is transformed under pressure and high heat to a hard, insoluble and infusible condition, for instance, paper impregnated with a varnish or other solution of phenolic resin. In the preferred form of our invention, we place also a number of such sheets similarly impregnated, below the board so as to coat both sides thereof. This aggregate of sheets and board we place between the hollow platens of a press of the well known type (see, for instance, patent to Sutherland, No. 1,506,509 dated August 26, 1924) If only one side of the board has been provided with the impregnated sheets of paper, we place between such side and the corresponding platen a piece of sponge board, preferably one impregnated with a fluxing inder, for instance, a board of the same size and material as the compacted board which is to be coated, and preferably of the same thickness as was the latter while in spongy condition. If both sides of the compacted board are to be covered with impregnated sheets of paper we place a suitable piece of sponge board between each side of said board stearic acid. Steam or other heating medium is thenadmitted to the platen chambers and do will not yield to any substantial degree when sulllapected to transverse compression forces.

damage to the board or resin coatin As the result of the application of heat and pressure, the resin has not only been converted into its final condition but caused to adhere firmly to the board.

The outermost layer of paper may, prior to the ap lication .of the resin be provided with a suita le design, for instance, a reproduction of a colored fabric, and this will be visible through the outermost resin layer andadd to the artistic effect of the finished article. Al-

though in accordance with our invention only one side of the board need be coated in the manner described, we prefer to coat both sides thereof so as to prevent any warping of the board which might be caused by the entrance of moisture or by stresses set up in the resin layer, on one side of the board, which would have no counterbalancing stresses on the other side of the board.

The sponge board is sufliciently elastic to act as a cushion. to compensate for any unevenness in the surface of the platen or platens, as the case maybe, or of the base board. Any unevenness in any such surface, for instance, of even 1/5000 inch, would cause an unevenness of finish and thus render the resulting product unsalable for any use in which the beauty of such product is important. It is a further very great vpractical advantage of our invention that the sponge board, after having performed its function as a cushion, becomes the compacted board ready in its turn to be coated with resin in the manner described with the aid of another piece of sponge board. The heat and pressure necessary to complete the hardening of the resin are usually suflicient to fuse the binder in the sponge board, and to compact such board; but in any event, enough heat and pressure are used to effect both such results.

It is obvious that the sponge board must possess suflicient elasticity while the resin hardens to accomplish the object described. Of course, the sponge board will lose its elasticity as it reaches its compacted condition, but by that time its function as an elastic cushion will have been performed. A further advantage of using as a cushion a sponge board provided with a fiuxing binder is that such binder is a very good conductor of heat, and thus readily conducts heat, during the pressure stage, from the platen to the resin, and, during the cooling stage, from the coated board to the platen.

In the accompanying drawings illustrating our invention, and in which Fi 1 shows the sponge board, base board, and s eets of pa er before compression, and Fig. 2 the same a ter compression, A, B show the two platens of a. press, each provided with a steam chamber, C represents a sheet of compacted pulp board made with a fusible binder, D-D represent pieces of sponge board, EE each represents a number of sheets of paper coated with resin, and F-F represent steel plates which prevent adhesion between the sponge board and its adjacent'resin la 'ers. If a resin coatin possessing a high g oss is desired, the steel plates are given a high polish on the side which comes into contact with the resin. If a resin covering with a mat or lustreless surface is desired, the steel plates are given a corresponding finish.

In order further to insure the sponge board, when the binder has been fluxed by the heat, against sticking to the steel plate, in order to prevent the refluxed binder of the compacted board from oozing into the resin and discoloring it, and in order to secure the strongest possible adhesion between the board and the resin coating, it is advantageous to impregnate the surface or surfaces, adjacent to the steel plate or plates, before using the sponge board as a cushion, with a liquid artificial'resin, for instance, by dipping the sponge board into a varnish made of such resin. The sponge board, after compaction will then be coated with a layer of finishe (insoluble and infusible) resin extendin into, and interlocking with, the fibres at and near the surface of the compacted board. This layer will prevent any tendency of the binder to stick to the steel sheet, and flow into the resin surrounding the sheets of paper.

Instead of paper, we may use any other suitable material in sheet form, such as cloth or felt, capable of absorbing fluid artificial resin. For instance, the outermost sheet may be constituted of a piece of cloth woven or printed in colored 'design. We may also have the same design appear on all the sheets so that if the outermost layer is worn through, or otherwise damaged, the appearance of the next layer maybe in harmony with the re mainder of the outermost layer.

We claim:

The process which consists in superim osing, in order, on one face of a base boar of compressed fibres intermlngled with a fluxing binder, one or more sheets of fibrous material embedded in fluid artificial resin, a

ing binder and being sufficiently elastic to act as a cushion to compensate for any'unevenness in the surface of the base board 'or'of the platen or platens with which such sheets of .fibrous material are to come in contact' thereafter subjecting the entire aggregate of boards and sheets to heat and pressure suflicient to render the resin infusible and insoluble and to compact the sponge board thus rendering such sponge board suitable for use as a base board, and then coating said board with resin in the manner aforesaid, thereby again producing a compacted sponge board suitable for treatment as a base board in the manner aforesaid.

HAROLD C. HARVEY, ERT L. BECHER. 

